In producing continuous glass filaments, it is conventional to flow individual streams of molten glass from closely spaced orifices in the bottom wall of an electrically heated platinum alloy feeder or bushing. Apparatus associated with the feeder draws or attenuates the streams into filaments which may be either continuous or discontinuous.
There are two types of continuous filament feeders in general use: a first, conventional, more widely used type employs a bottom wall having stream emitting orifices provided at orificed projections or tips jutting from its exterior surface; a second, more recently developed, type uses an orificed bottom wall having a planar exterior surface. The first former type is known as a "tipped" feeder, and examples are disclosed in Russell Pat. No. Re. 24,060 and in Glaser et al Pat. Nos. 4,222,757 and 4,321,074. The second type is known as a "tipless" feeder, and an example of such a feeder or bushing is disclosed in Strickland Pat. No. 3,905,790.
A third type of continuous filament feeder utilizes enlarged depending "tips", each provided with multiple orifices which are "tipless". Thus, this feeder is a hybrid "tipped-tipless" feeder.
Heretofore, tipless type feeders flooded at start-up and during filament formation upon a filament break. Flooding makes feeder start-up slow and interrupts filament formation once the filament attenuation operation is begun. In contrast, tipped type feeders are not as prone to flooding. The orificed projections of tipped type feeders isolate at their end regions the individual emitted molten glass streams, and thus impede the movement of the molten glass to flood the exterior surface of the bottom wall. Tipless feeders do not incorporate this stream isolating geometry.
These various types of feeders have been harried by glass beads dropping into the "veil" of filaments during filament attenuation. When a filament breaks during filament attenuation, molten glass oozes from the orifice associated with the broken filament; the molten glass forms a small glob or bead that enlarges until its mass causes it to fall away from the orifice into the filaments being attenuated. Like flooding, bead drops interrupt filament production. Even a single bead drop entering the veil causes additional fibers to break, and the resultant forming interruption occurs successively until the entire feeder must be restarted.